U.S. prosecutors had argued Xcel ignored safety rules requiring a rescue plan to be in place for the workers, and failed to take other precautions to protect the men as they worked in a closed-off space, The Denver Post reported.
The companies faced five counts of willfully violating Occupational Safety and Health Administration regulations causing death, all stemming from an October 2007 fire at Xcel's Cabin Creek power plant near Georgetown, Colo. The fire happened as workers from RPI Coating Inc., a California industrial painting firm, were resealing the inside of a large, drained water pipe called a penstock.
The defense had argued the fire was an unforeseeable accident and said RPI was responsible for the men's safety, the Post said.
OSHA Regional Administrator Greg Baxter said in a statement that he was disappointed in the verdict.
The report said OSHA targeted Xcel and RPI in 2008 with nearly $2 million in combined fines for safety violations involving the fire. Xcel also paid millions to the victims' families to settle civil lawsuits.
Notable deaths of 2014 [PHOTOS]